When the Australian Chamber Orchestra plays in unison, it sounds like what it is: a lot of instruments playing together. Not for this group the polish, or masquerade, of many voices sounding as one. Instead, you get many voices sounding like many: an energetic chorus, with a slight burr and warmth, conveying a visceral thrill every time they plunge together into a work after the downbeat from its violinist-leader, Richard Tognetti.

Indeed, the ACO, which on Tuesday opened the season of the Kennedy Center's Fortas Chamber Music Concerts, offers some of the energy and vibe of a rock band with the ability of a crack classical chamber group. Its freshness is remarkable. The young players all perform standing (except, of course, for the cellists), which seems to allow a greater physical connection to the music -- although it's hard to imagine that even seating this bunch would do much to rein them in. To look at the ensemble, you would never suspect it had been formed in 1975; Tognetti, himself a youthful-seeming elder statesman, took over as artistic director in 1990 at the age of 25, and appears to be the oldest person onstage.

Young energy doesn't have to mean in-your-face rebellion against the classical music status quo. It's true that the ensemble's second program this week, scheduled for Wednesday night, includes an arrangement of "Shine On, You Crazy Diamond" from Pink Floyd's 1975 album, "Wish You Were Here." But Tuesday's program was straight-ahead classical; the only twist was the quality of energy that came through in the playing. Indeed, the program was downright conservative if measured against Pink Floyd standards.

Conservative, however, is not the best way to describe an evening that juxtaposes bracing Handel, Elgar (one of the rare times in performance history when "bracing Elgar" was not an oxymoron) and Bart?k with a string-quartet arrangement by the 54-year-old Australian composer Carl Vine, and a couple of brief concerto-like pieces for solo violin (Tognetti's own arrangement of Ravel's "Deux M?lodies H?braiques") thrown in for good measure. Tognetti seems to come up with consistently vital, interesting programming.

The very first piece, the seventh Concerto Grosso of the 12 that make up Handel's Op. 6, showed a thoughtful match of players and work. The repeated bow strokes that marked the start of the canon, in each voice, underlined the particular rough, taut energy of this group's sound and the no-frills brand of musical gutsiness that was to characterize the concert as a whole.

That's not to say the players aren't capable of delicacy as well, such as in the string solos that dominated the slow central movement of Vine's piece, called "Smith's Alchemy." This was a muscular and wide-ranging piece of pleasing if slightly ingratiating solidity, with more than a few overtones of Prokofiev in the roughly dancing tunes above bitter sawing rhythms in the first movement.

The weak spot on the program was a bonbon: Tognetti's arrangement of the fifth Paganini Caprice, which he prefaced with a few remarks that placed it in the same aesthetic territory as the avant-garde cuisine of restaurants like El Bulli or the Fat Duck: an unexpected transformation, like egg-and-bacon ice cream. The result was both fiendish and pleasant, but -- as played by Tognetti and Satu Vanska, backed by the remaining players -- not quite clean or in tune enough to feel like the virtuosic showpiece it represents.

The Paganini was perhaps a nod to a notable absence on the program: There was no featured soloist, apart from Tognetti. The group has often toured in the past with big-name artists. On Tuesday, the group itself was sufficient highlight -- as it abundantly demonstrated in Bart?k's Divertimento for Strings, a powerful and moving finish.